NP Mars

[Dave Monroe]

From, e.g., W. Wayt Gibbs and Corey S. Powell, "Bugs
In The Data? The Controversy over Martian Life is Just
Beginning," Scientific American (October 1996), pp.
12-3 ...

"NEW HINT OF LIFE IN SPACE IS FOUND: Meteorites Yield
Fossilized, One-Cell Organisms Unlike Any Known on the
Earth," shouted a headline in "The New York Times."
"Something Out There," chimed in"Newsweek." Respected
scientists told crowds of reporters that their work,
published in a prestigious journal, revealed complex
hydrocarbons and what looked like fossilized bacteria
buried deep within a meteorite. This, they claimed,
provided "the first physical evidence for the
existence of forms of life beyond our planet."

That was 1961. And the meteorite in question was not
the one from Mars that has made recent headlines but
another that had fallen a century earlier in Orgueil,
France. Under closer scrutiny, the astonishing
evidence was eventually thrown out of the court of
scientific opinion. The organic chemicals and
"fossils" turned out to be ragweed pollen and furnace
ash. 

So it is with understandable skepticism that
scientists are greeting the bold assertions, made by
David S. McKay of the National Aeronautics and Space
Administration Johnson Space Center and eight
colleagues, that the peculiar features they found in
meteorite ALH84001 are best explained by the existence
of primitive life on early Mars. Despite public
enthusiam about the conclusions, published in Science,
many leading researchers who study meteorites and
ancient life have weighed the evidence and found it
unconvincing. "There are nonbiological interpretations
of McKay's data that are much more likely," says Derek
Sears, editor of the journal Meteoritics and Planetary
Science.

On August 7 the nightly news recounted ALH84001Us
impressive resume: born 4.5 billion years ago in
Mars's depths; splashed by a huge impact into
interplanetary space to drift for 16 million years;
captured in Earth's gravity and dragged into Antarctic
snow; buried in ice for 10 to 20 millennia until 1984,
when meteorite hunters, trudging seven abreast across
the Allan Hills ice flow, picked it up and made it
famous. That much nearly everyone agrees on; the
controversy centers on the rock's less glamorous
inside story.

McKay and his collaborators build the case for life on
four lines of evidence. The first are orangish blobs,
no bigger than periods, that dot the walls of the
cracks and crevices perforating the meteorite's shiny
crust. These multilayered formations, called carbonate
rosettes, tend to have cores rich in manganese,
surrounded by alternating iron- and magnesium-enhanced
layers and a rind consisting primarily of magnetite.
Bacteria in ponds can produce similar rosettes as they
metabolize minerals. But "that is a perfectly
reasonable sequence to find in a changing chemical
environment as well," counters Kenneth Nealson, a
biologist at the University of Wisconsin, who was one
of the paper's peer reviewers.

The second line of evidence centers on the discovery
of organic compounds called polycyclic aromatic
hydrocarbons, or PAHs, in and around the carbonate.
Richard N. Zare, a Stanford University chemist and
co-author of the Science paper, reports that the rock
contains an unusual mixture of certain lightweight
PAHs. "In conjunction with all the other data, it
seems most likely to me that they all came from the
breakdown products of something that was once alive,"
he says.

Critics suggest other possible explanations,
however....

[...]

Beneath all these thoughts lies a nagging question:
Will we even know life if we see it? Some
unconventional thinkers such as Thomas Gold of Cornell
University and English astronomer Fred Hoyle have
suggested that life may exist in unlikely
environments, such as cometary nuclei or the crust of
the moon. Even identifying carbon-based life is
ferociously difficult--what if some life follows
unconventional chemistries? "It boggles the mind to
think of these questions," reflects Miller. "You have
to stick with what you know; the alternative is
sitting around, looking at your navel."

If the results reported by McKay's group hold up,
Miller suspects it will be just the tip of the
iceberg. "My impression is that bacterial life exists
on planets around one in 10 stars, maybe more," he
speculates. "I would view life on Mars not as a
surprise but as a new frontier."

http://www.sciam.com/explorations/081996explorations.html

http://www.sciam.com/1096issue/1096infocus.html

I skipped past a LOT of material here, so ... and the
evidence against, as time wore on, only mounted, but
... but worth simply searching "Mars" on the SciAm
site ...

http://sciam.com/

All sorts of things perhaps of interest come up ...

--- Cat Hamilton <cat_hamilton at hotmail.com> wrote:
> Scientists found life there back in like...August of
> 1997, I think.  Doesn't anyone remember this?  I
> wish I had a link...



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